Soft tissue sarcomas (STS) are a group of rare malignant tumours arising from mesenchymal cells, which can occur at any age, and have no significant gender difference, and have a wide distribution and different histological appearance. Although the proportion of STS is less than 1% in adult malignant tumours and 15% in childhood malignant tumours, about 50% STS patients would have distant metastasis, even death.
The pathogeny of soft tissue sarcomas is still unclear, it is generally believed that soft tissue sarcomas is caused by many factors, and currently, it is known that a small number of genetic factors have a correlation with pathogenesis of certain soft tissue sarcomas. The progress of STS is a course gradually spreading from local portion(s) to the whole body, characterized by tumidness and/or deep masses. The local period of soft tissue sarcomas occurred in adult patients or some children patients has a longer duration. The most frequently metastatic site is lung, followed by bones, liver, etc., whereas regional lymph nodes are less involved.
Common soft tissue sarcomas include malignant fibrous histiocytoma, fibrosarcoma, liposarcoma, leiomyosarcoma of soft tissue, rhabdomyosarcoma, and synovial sarcoma. Other soft tissue sarcomas also include dermatofibrosarcoma protuberans, malignant peripheral nerve sheath tumor, alveolar soft-part sarcoma, clear cell sarcoma, hemangiosarcoma, malignant mesenchymoma, epithelioid sarcoma, undifferentiated sarcoma and the like.
Malignant fibrous histiocytoma (MFH) is the sarcoma arising from tissue cells, generally consisting of both of tissue cells and fibroblast.
Fibrosarcoma is a malignant tumor consisting of fibrocyte and fiber produced thereby, and has a relatively single morphology and herringbone structure.
Liposarcoma is a soft tissue malignant tumour, characterized by differentiation of tumour cells to lipoblasts and manifesting as the existence of atypical lipoblasts in different differentiation stages.
Leiomyosarcoma of soft tissue is a malignant tumour occurred in smooth muscle cells or mesenchymal cells having differentiation potential to smooth muscle cells.
Rhabdomyosarcoma (RMS) is a soft tissue malignant tumour arising from primary mesenchymal cells differentiating into striated muscle, and consisting of different differentiation grades of striated muscle metrocyte. The incidence of rhabdomyosarcoma is higher in male than in female. The onset age range is quite considerable, and it could onset from the newborns to the elderly, most frequently in children. Rhabdomyosarcoma is the one having higher malignancy in soft tissue sarcomas with a poor prognosis.
Synovial sarcoma (SS) is a malignant tumour in which the tumour cells show two-way differentiation, wherein epithelioid cells form cleft and atypical glandular cavity, and spindle cells generate reticular fibers and collagen fibers. The incidence of synovial sarcoma in soft tissue sarcomas is in the middle level.
Alveolar soft-part sarcoma (ASPS) is a soft tissue malignant tumour with uncertain histogenesis, and it has unique histological appearance of pseudo secretory-like structure showing alveolar and is a rare tumour.
Currently, the treatment of soft tissue sarcomas emphasizes multidisciplinary synthetic therapy primarily based on surgery. Surgery or the combination with radiotherapy is the main treatment method of soft tissue sarcomas with low-grade malignancy, while as for the patients with advanced soft tissue sarcomas having distant metastasis, chemotherapy is the main method for treatment. Since STS frequently spread into the whole body and pulmonary metastasis may occur in its early stage, surgery is still recommended for isolated pulmonary metastasis focuses, other metastasis focuses need drug therapy. It is especially important to select appropriate drug therapy for patients with advanced refractory STS being unsuitable for surgery or having tolerance to commonly used chemotherapy drugs.
At present, there are a few chemotherapeutics effective against STS, including anthracyclines, such as adriamycin, doxorubicin, epirubicin, pirarubicin and the like; and alkylating drugs, such as cyclophosphamide, ifosfamide, decarbazine and the like. The effective rate of single drug is 14%-30%. Adriamycin and ifosfamide show the best therapeutic effect for first-line chemotherapy. Although all the above drugs can effectively treat STS, the following factors such as safety and tolerance of the drugs limit the application of such drugs in treating advanced, relapsed and refractory STS, and there is an urgent clinical need to develop new second-line drugs for treatment of STS.
In April 2012, the FDA approves Pazopanib (Votrient) of GSK for use of treating patients with advanced soft tissue sarcomas who have been treated with chemotherapy.

Since soft tissue sarcomas is a rare heterogeneous group of tumours, treatment is usually more complex, the drugs and the programs for treatment available are limited yet, thus developing more new therapeutic drugs having strong specificity, target specificity, little side-effect and significant efficiency is required, so as to achieve desirable therapeutic effects.